This invention relates generally to construction machines such as hydraulic power shovel type excavators and the like, and more particularly to a cab for a construction machine, providing a reinforced operating room for an operator at the control of the construction machine.
In the case of hydraulic power shovel type excavators, a crawler- or wheel-type drive is mounted on a frame of a vehicular base carrier, and an upper rotary body is mounted on the base carrier through a rotary mechanism. Further, a front working mechanism is mounted on top of the upper rotary body to perform ground excavating operations. The front working mechanism is largely constituted by a boom, an arm and a front attachment. For a ground excavating operation, a bucket is attached to the arm. The base end of the boom, which constitutes the front working mechanism, is pivotally supported on the upper rotary body, and lifted up and down by means of a hydraulic cylinder. The arm is pivotally supported on a fore end portion of the boom and turned up and down relative to the boom by means of a hydraulic cylinder. The bucket as a front attachment is connected to a fore end portion of the arm through a link mechanism and turned toward and away from the arm similarly by means of a hydraulic cylinder.
The operations of the hydraulic power shovel type excavator, including drive of the vehicular base carrier, rotations of the upper rotary body by the rotary mechanism and operations of the front working mechanism, are controlled by an operator on the upper rotary body. For this purpose, a cab is provided on the upper rotary body, and an operator""s seat to be seated by an operator is provided in the cab, along with operating levers or other operating means. In order to operate the excavator smoothly, it is necessary for the operator to have a broad view field on each side. More particularly, it is necessary for the operator to have a wide view field not only on the front and rear sides of the cab but also on the right and left sides and, in the case of a ground excavating operation, in downward and upward directions. In this regard, a wide and clear view filed needs to be secured especially in directions forward of the cab, including obliquely upward or obliquely downward directions. Therefore, the front side of the cab is almost entirely constituted by an window or windows. In some cases, a top window is provided in the roof of the cab continuously from a front window.
A cab is mounted on the upper rotary body of the excavator. Considering vibrations which are transmitted to the cab while the hydraulic power shovel type excavator in operation and possibilities of collisions against a nearby structural body, rocks or trees, the cab should have high strength as a structure. Normally, a cab is constituted by an enclosure including front and rear sections, right and left side sections and a roof section. A door is provided in one of the side sections of the cab to permit an operator get into and get out of the cab, and the other side section is located in a position in the proximity of a front working mechanism. A plural number of pillars are erected in the right and left side sections, and beams are bridged between the respective pillars. Normally, the pillars and beams are each constituted by a steel plate which is formed in a hollow columnar shape, and, for example, are assembled integrally with each other in the shape of an inverted U-shape. Accordingly, each side section of the cab is constituted by a frame structure which is composed of pillars and a beam member, and either a door or a window is fitted in the frame structure. The cab has a similar frame structure on its rear side. Thus, it is primarily the side and rear frame structures on the right, left and rear sides of the cab that contribute to the structural strength of the cab itself. The roof section of the cab is also constituted by a steel plate, but hollow panel structures are employed in some cases to increase the strength of the roof section.
As already explained hereinbefore, on the front side, the cab enclosure is provided with a large window, which occupies almost the entire areas of the front section, for the purpose of ensuring a wide view field in forward directions. Therefore, in a case where a top window is additionally provided in the roof section for securing a view field in upward directions, the cab inherently has weak points in transitional portions from the front section to the roof section, as compared with other portions of the cab. In order to avoid this problem, a transverse or cross beam is bridged between the two side sections and in a transitional portion from the front to the top window for reinforcing purposes. This reinforcing transverse beam of this sort however will block a view field of an operator in the cab to a considerable degree if its thickness is increased from the standpoint of enhancing the strength of the cab.
Therefore, it is desirable to impart necessary strength to the cab by increasing the strength of the frame structures of the side and rear sections instead of providing a thick reinforcing member in transitional portions from the front to roof window of the cab. This approach makes it possible to prevent the cab from easily undergoing crucial deformation or damages when impacts of certain magnitudes are externally applied thereto, while securing a broader view field for the operator both in forward and upward directions.
In operation, a hydraulic power shovel type excavator is often required to run on rough terrains with undulations and sporadically spotted with mounds and dimples. Therefore, the excavator can lose its balance while running on such a rough terrain. In the case of a crawler type excavator having a crawler type drive means on the vehicular base carrier, it is unlikely for the machine to fall down on its side even if it loses balance while in travel, because crawler belts have broad treading surface areas. However, the machine can fall down under certain circumstances, for example, in a case where the machine itself is ill-balanced and erroneously operated by an operator.
A front working mechanism is provided on an upper rotary body of an excavator, on one side of a cab, normally on the right side of a cab, when seen by an operator who is seated forward on an operator""s seat in the cab. Therefore, when an excavator happens to fall down to that side, there is little possibility of a falling load acting directly on the cab. However, should an excavator fall down to the opposite side, it is likely that a falling load of extremely large magnitude acts directly on the cab. In addition, in the case of a hydraulic power shovel type excavator having a cab and a front working mechanism at a close distance from each other for the purpose of minimizing the width of the machine, one side of the cab is subjected to impacts of collision against the ground and as a result the other side of the cab is collided against a closely opposing side of the front working mechanism. Therefore, on such an occasion, the cab is crushed and deformed from opposite sides easily if a falling load is imposed on a transitional portion between front to top windows of the cab where the strength against a lateral load is relatively low.
With the foregoing situations in view, it is an object of the present invention to provide a cab for a construction machine, employing a reinforcing means in its structure to impart high strength and shape retainability to the cab for preventing crucial deformation or collapsing even in the event the cab is subjected to a load of a large magnitude like a falling load, while guaranteeing a wide view field for an operator in the cab.
It is another object of the present invention to provide a cab for a construction machine like a power shovel type excavator, which can protect an operator in the cab safely even when the excavator happens to fall down on a ground while in operation.
In accordance with the present invention, for achieving the above-stated objectives, there is provided a cab for a construction machine, being mounted on an upper rotary body of the construction machine along with a working mechanism and providing an operating room within an enclosure consisting of a first side frame structure containing a door to be opened and closed by an operator, a second side frame structure located on the side of the working mechanism, a front section provided between front ends of the first and second side frame structures and substantially entirely occupied by a front window, a roof section, and a rear section, characterized in that the cab comprises: a cross beam member bridged between upper front corners of the first and second side frame structures to extend along upper side of the front window; and a reinforcing beam member provided between the first and second side frame structures for reinforcing the cross beam member.
In a case where the roof section is provided with a roof window in a front portion thereof, preferably the cross beam is located in boundary regions between the front and roof windows. The reinforcing beam member should be located in a position where it will not block a view field of an operator in the cab to any objectionable degree. In this regard, preferably the reinforcing beam member is in the shape of a rod and located substantially in parallel and overlapping relation with the cross beam member. By so arranging, the reinforcing beam member can be substantially concealed behind cross beam member without blocking a view field of an operator when the operator who is seated on an operator""s seat in the cab looks up in an obliquely upward direction toward the cross beam member between the front and roof windows of the cab. The opposite ends of the reinforcing beam member are securely connected to the first and second side frame structures. In a preferred form of the invention, the reinforcing beam member is bridged between brackets securely fixed to a front or lateral side of foremost pillars of the first and second side frame structures. The reinforcing beam member which is provided on the outer side of the cab can be for mounting accessories of the construction machine, for example, accessories such as lighting lamp assemblies, mirrors, protector covers for dropping rocks or stones, sun shades, wipers etc. In a case where the cross beam member is constituted by a hollow columnar structure, the reinforcing beam member can be passed through an internal hollow cavity of the cross beam member. In any case, the reinforcing beam member should have high bending strength. Preferably, the reinforcing beam member is constituted by a metal pipe of a circular shape or triangular, square or other polygonal shape in cross section. In order to enhance the bending strength, a foaming resin such as foaming urethane can be filled in the internal cavity of the pipe.